When people perform astronomy observation, the position of the celestial target often rotates with respect to the refracting astronomical telescope. Therefore, the current refracting telescopes need to be equipped with a certain accessory, i.e., diagonals, which could change the optical axis orientation, thus will facilitate the observers' viewing celestial targets in different positions. At present, two kinds of diagonals with fixed angle are commonly used. One is 45°, the other is 90°, which could turn the optical axis by 45° or 90° for convenient observation. Since the viewing angle is fixed, the whole diagonal has to be changed if the observers want to change the observation angle, which will cause the problems of redundant accessories and wasting time to re-aim the target.